Cancelation of MTN policy

I've canceled my MTN month to month data package since February 2021 stating i no longer wish to proceed receiving data from them stating financial difficulties, but every month they've been debiting till today August 2021 and ended up reversing my money...now they are threatening me with legal action of which i don't understand why because I'm no longer even using the modem since January 2021...I'm so tired and disappointed by MTN RSA